Library Mode: esm is not minified but cjs and umd are minified

[guoyunhe]

Describe the bug

In Library Mode, we usually expect that the output (CJS, ESM, UMD) are not minified. This is easier for debugging when developing applications.

ESM looks good:

function foobar() {
  console.log("foobar");
}
export { foobar as default };

But vite will minify CJS and UMD:

"use strict";function o(){console.log("foobar")}module.exports=o;

(function(e,o){typeof exports=="object"&&typeof module!="undefined"?module.exports=o():typeof define=="function"&&define.amd?define(o):(e=typeof globalThis!="undefined"?globalThis:e||self,e.Foobar=o())})(this,function(){"use strict";function e(){console.log("foobar")}return e});

I know build.minify: false can turn this off. But it is better to make it automatic.

Reproduction

https://stackblitz.com/edit/vitejs-vite-fdafhp?file=vite.config.js,index.js,dist%2Fvite-starter.cjs.js&terminal=dev

System Info

System:
    OS: macOS 12.4
    CPU: (12) x64 Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz
    Memory: 798.25 MB / 16.00 GB
    Shell: 5.8.1 - /bin/zsh
  Binaries:
    Node: 16.14.0 - /usr/local/bin/node
    Yarn: 1.22.17 - /usr/local/bin/yarn
    npm: 8.3.1 - /usr/local/bin/npm
  Browsers:
    Chrome: 103.0.5060.53
    Edge: 103.0.1264.37
    Firefox: 100.0.2
    Safari: 15.5

Used Package Manager

npm

Logs

No response

Validations

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• The provided reproduction is a minimal reproducible example of the bug.

[bluwy]

Minify is intentionally on by default in lib mode. es is not minified as it messes with tree-shaking, though partial minification is supported in Vite 3 with #8811. There's also #6555 to completely minify regardless of treeshaking issues. If minifying is not desirable, build.minify: false should be set.

[songlairui]

not a bug.

minify has no effect for build phase,
rollupOptions.compact only effect module wrapper, rollup-doc output.compact

you can minify by rollup plugin

vite.config.ts

import { terser } from "rollup-plugin-terser";

export default defineConfig(() => ({
  build: {
    lib: {
        entry: '...',
        formats:['es']
    },
    rollupOptions: {
        // only for build phase, # https://vitejs.dev/guide/api-plugin.html#rollup-plugin-compatibility
        plugins: [terser()],
    }
  }
}))